1. Field of the Invention
This invention relates to video processing. In particular, the invention relates to video muting.
2. Description of Related Art
Video recording typically involves many pieces of video equipment including video player and video recorder. Each equipment may have its own format and different data processing requirements. A video format may work with one machine for random video segment access but does not work with another machine from another different manufacturer during video playback.
For example, some video equipment uses pulse code modulation (PCM) index decoding to locate video segments on video track during playback. Some other equipment may just locate the video segments by identifying blank segments or gaps. A video tape recorded in one format therefore cannot be used with machine requiring a different format for random segment access.
Therefore, there is a need to have a technique to allow a video recorder to generate a video tape that can be used in both types of playback machines during random segment access by manipulating the timing of the gap and PCM index data.
The present invention is a method and apparatus to control muting a video output. A tone detector detects a first tone in a control tone signal generated by a video player during playing a video program from a master medium. The control tone signal is recorded on the master medium. The video player provides a video signal corresponding to the video program. A mute controller mutes a video output representing the video signal when the first tone is detected. The video output is recorded on a duplication medium in a video recorder.
In one embodiment, the tone detector includes a bandpass filter, a rectifier, and a DC level detector. The bandpass filter passes the first tone. The rectifier rectifies the filtered first tone. The level detector detects a trigger level provided by the rectified audio tone, the trigger level indicating presence of the first tone. The mute controller includes a timer, a video input buffer, a video output amplifier, and a switch. The timer asserts a switch control signal having a mute interval when the trigger level is detected. The video output is muted during the mute interval. The video input buffer buffers the video signal. The video output amplifier receives the video signal and provides the video output. The switch attenuates the video signal according to the switch control signal. The attenuated video signal corresponds to the muted video output.